1. Field of the Invention
The present invention relates to a laser scanner.
2. Description of Related Art
Suggested in a conventional field of a laser scanner, for example, as shown in JP-A-2006-227044, is technology of deflecting, with a deflector (for example, resonance mirror), laser light transformed into convergent light in a main scanning direction and then condensing it onto a surface to be scanned with a scanning lens that has a negative refractive power (optical power) in the main-scanning direction and having arcsine property to thereby scan the surface to be scanned at a constant speed. As in JP-A-2006-227044, with configuration such that convergent light is made incident on the deflector in the main-scanning direction and the scanning lens has a negative refractive power in the main-scanning direction, even with a small angle of deflection by the deflector, the distance from the deflector to the surface to be scanned required for obtaining a desired scanning width in the main-scanning direction can be reduced, thus permitting downsizing of the device.
However, in a conventional laser scanner, in a case where the number of scanning lenses used is one, the sub-scanning magnification is not uniform in the main-scanning direction, thus causing, for example, upon high-speed drawing with a plurality of beams, a problem of deteriorated image quality due to a change in the interval in a sub-scanning direction between the plurality of beams (irradiation spots) depending on the position thereof on the surface to be scanned.